package com.demo.lock.aqs.exclusive;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

public class Mutex implements Lock{

	@Override
	public void lock() {
		sync.acquire(1);
	}

	@Override
	public void lockInterruptibly() throws InterruptedException {
		sync.acquireInterruptibly(1);
	}

	@Override
	public boolean tryLock() {
		return sync.tryAcquire(1);
	}

	@Override
	public boolean tryLock(long time, TimeUnit unit)
			throws InterruptedException {
		return sync.tryAcquireNanos(1,unit.toNanos(time));
	}

	@Override
	public void unlock() {
		sync.release(1);
	}

	@Override
	public Condition newCondition() {
		return sync.newCondition();
	}
	
	private final Sync sync=new Sync();
	
	private static class Sync extends AbstractQueuedSynchronizer{

		private static final long serialVersionUID = 3922266586770237703L;

		@Override
		protected boolean tryAcquire(int arg) {
			if(compareAndSetState(0,1)){
				setExclusiveOwnerThread(Thread.currentThread());
				return true;
			}
			return false;
		}

		@Override
		protected boolean tryRelease(int arg) {
			if(getState()==0){
				throw new IllegalMonitorStateException();
			}
			setExclusiveOwnerThread(null);
			setState(0);
			return true;
		}

		@Override
		protected boolean isHeldExclusively() {
			return getState()==1;
		}
		
		Condition newCondition(){
			return new ConditionObject();
		}
		
	}

}
